Illegal copying aid distribution of multimedia content (audio and video) is prevalent in recent years, especially using the Internet. This illegal copying and distribution is an infringement of copyright protection laws and cause financial damages to the rightful owners of the content. It is therefore of great interest to find methods that would stop or at least reduces illegal copying and distribution of multimedia files without offending rightful usage.
Methods for usage rights enforcement of digital media, such as video or audio are known. Some of these methods of enforcement require unique digital watermarks to be embedded into each copy of the media at the source, prior to its distribution to an authorized party. If usage of the content by an unauthorized party is identified, the identity of the authorized party who originally received the content is readily determined from the unique embedded digital watermark.
Other methods use watermarks and steganograms for digital rights management (DRM). In this case, substantially imperceptible information is embedded in the digital content. This information is able to certify usage rights regarding the digital content.
Methods for embedding substantially imperceptible messages in the form of watermarks or steganograms into content are well known. However, since watermarks should be embedded into the digital media content in a manner that does not reduce the quality of the media, it is hard to maintain robustness against malicious attempts to remove the watermark as well as against various changes to which the digital content is subjected while using legitimate digital processing and compression. In particular, it is hard to maintain robustness against averaging of several copies, where each copy contains a different watermark.
PCT application number IL01/00923 describes a method for efficient on-line, real-time watermarking of video and/or audio and/or other digital content. The method, dubbed “watermark by selection”, is based on first selecting salient fractions of the content, whose removal will greatly reduce the quality of the content, then dividing each of the fragments into several segments. Each segment is then replicated N times, and each copy is marked with a special steganogram that preferably cannot be perceived by a human but can be detected by the embedder (or a suitable reader). Each replicated segment is viewed as “alphabetic symbols”. On-line, real-time watermarking is based on first encoding the desired message using the above alphabetic symbols, and then selecting between alternative copies that correspond to the symbols in order to produce the analog of the desired sequence of symbols. This basic scheme can thereafter be augmented with error correcting codes and error resilience methods. However, the security of the method relies on the underlying watermarking scheme, i.e., the method by which various steganograms were embedded in the various segments.
Various attacks against watermarks are known. Malicious attacks attempts to render the watermark undetectable, e.g., by using various image-processing methods and/or averaging of several instances with different embedded steganograms. Recompression of the video with different codecs and various frame-rates also render many of the current watermarking methods ineffective.
There is thus a recognized need for, and it would be highly advantageous to have, a method and system that allow robust embedding of watermarks and steganograms in digital video, which will overcome the drawbacks of current methods as described above.